Application of Picric Acid Solution Containing High Concentration Corrosion Inhibitor in Direct Etching Test of Austenite Grain Size

Picric acid is one of the most common metallographic etching agent in direct corrosion test of austenite grain size. In order to inhibit the corrosion rate of the intra crystalline structure, corrosion inhibitors are usually added to the formula. Sodium dodecyl benzene sulfonate was selected as corrosion inhibitor. By adjusting the ratio of corrosion inhibitor, the test methods of austenite grain size including partial quenched and high temperature tempered structure, completely quenched and high temperature tempered structure and granular bainite structure were carried out. The results show that increasing the content of corrosion inhibitor can effectively inhibit the corrosion rate of the intra crystalline structure. Longitudinal test of austenite grain size in the banded segregated zone can rapidly corroded austenite grain size of the completely quenched and high temperature tempered samples. Picric acid solution containing high concentration corrosion inhibitor was proved to be a general corrosion agent of austenite grain size.